Taste is made possible by the taste buds although smell does play a part in perceiving tastes. The different types of taste receptors or taste buds to detect different tastes. The four primary tastes were considered as sour, salty, sweet and bitter but now umami taste is also considered as one of the primary tastes. The variations in tastes of different foods is due to a combination of taste sensations being triggered.
Types of Abnormal Tastes
As with any sense, there can be a disturbance in taste. It can be dulled, totally absent, or be described as a strange taste or bad taste in the mouth. Depending on the cause, there may be reports of a sour, bitter or metallic taste. Dysgeusia is a broad term to describe any disturbance of the sense of taste. This may include :
- Ageusia : total loss of taste.
- Hypogeusia : diminished taste sensitivity.
- Parageusia : taste with no stimuli present.
- Cacogeusia : foul taste sensations.
Disruption of the sense of taste is not only due to problems with the taste buds and taste centers in the brain. The sense of smell, temperature and tactile sensation on the tongue may also influence the sense of taste. One of the common causes of dysgeusia is due to diminished smell (hyposmia) or even a loss of sense of the smell (anosmia).
However, in most cases a problem with the sense of taste is due to a problem in the mouth. Less commonly, taste sensation problems may be due to nerve or brain problems.
Causes of Dysgeusia
The causes below can cause a range of disturbances ranging from no taste (ageusia) or reduced taste (hypogeusia) to an abnormal bad taste (cacogeusia).
- Burns to the mouth usually caused by consuming vert hot food or beverages.
- Chemicals – medication and substances mentioned below, poisons, strong acids (including stomach acid in GERD), caustic agents
- Surgery – damage to cranial nerves or branches : facial nerve (CN VII), glossopharyngeal nerve (CN IX), hypoglossal nerve (CN XII)
- Hemorrhage (bleeding in the mouth, nose, esophagus) – metallic taste in the mouth
- Head trauma
- Orodenal problems
- Poor oral hygiene
- GERD (acid reflux)
- Eating disorders – repeated vomiting in bulimia can damage the taste buds.
- Neurological disorders like Parkinson’s disease and multiple sclerosis.
– Mouth – tongue, cheek, gums
– Upper respiratory tract – nose, throat and larynx
– Ear – particularly middle ear infections
– Dental – tooth cavity, gingivitis, dental abscess
– Systemic – HIV
- Drugs – certain antibiotics, antihistamines, CNS depressants / stimulants used in the treatment of various psychiatric disorders and insomnia.
- Alcohol, narcotics, cigarette smoking and nicotine replacement products.
- Chemotherapy and radiation therapy.
- Other disorders:
– Diabetes mellitus (diabetic neuropathy)
– Zinc deficiency
– Vitamin B12 deficiency
– Sjogren’s syndrome
– Kidney failure
What is Cacogeusia?
Cacogeusia is the medical term for a bad (foul) taste in the mouth. It usually exists on its own and does not necessarily occur when eating or tasting food or drink that does not otherwise taste foul. At times an altered taste sensation, known as dysgeusia, can make food or drink taste foul, although under normal circumstances it is not offensive tasting.
Causes of Bad Taste in the Mouth
The more common causes of cacogeusia are related to pathology in the mouth. Gastrointestinal causes and disorders of the lung and airways may also be responsible. Halitosis (bad breath) is often seen in these cases. In cacogeusia due to psychogenic causes and medication, halitosis is usually absent. If cacogeusia is accompanied by abnormal bad odors (cacosmia) then upper respiratory tract infections and sinusitis needs to be considered.
A tooth cavity is probably the most common cause of cacogeusia. The rotting food particles (decomposition) in the cavity causes a bad taste in the mouth and often bad breath as well. Gum diseases, like gingivitis and periodontitis, may also be responsible for a bad taste and bad breath.
Apthous ulcers (mouth sores), oral cavity cancer and other causes of stomatitis are also responsible for cacogeusia. A bad taste in the mouth may not be present at the outset and is usually seen in infectious causes. Conditions of the throat, like tonsillitis and pharyngitis, may also be responsible. Various causes of xerostomia (dry mouth) may result in cacogeusia but this is usually due to the increased risk of mouth and dental infections seen with reduced saliva production.
A number of conditions affecting the gastrointestinal tract may result in cacogeusia. This may either be related to decomposition of food due to impaired motility like in gastroparesis and pyloric stenosis, inflammation as is seen in gastritis and infections of the upper gut.
Severe cases of GERD (gastroesophageal reflux disease) may also be responsible as partially digested and sometimes decomposed food particles and stomach acid are passed up into the pharynx or mouth. This bad taste is often more prominent in the morning upon waking, and also results in a persistent sore throat in the mornings that ease during the course of the day as well as bad morning breath.
Conditions affecting the airways and lungs may also result in cacogeusia and usually halitosis as well. Most of the causes are infectious in nature. This includes a lung abscess, bronchiectasis and tuberculosis. There are usually other symptoms also present, such as a cough and difficulty breathing. Prompt medical attention is necessary as these lung problems can lead to serious complications.
- Certain medication like antibiotics, oral contraceptives and some PPIs (proton pump inhibitors) have been implicated in cacogeusia. However, in many instances this may be due to other factors and there is insufficient evidence to verify this as a side effect.
- Diabetic patients may report a bad taste in the mouth, although halitosis is a more common complaint, and it is usually related to ketacidosis. Infectious stomatitis and dental caries are more likely to occur in a case of uncontrolled diabetes which will result in both halitosis and cacogeusia.
- Psychogenic causes may also be responsible however, the above mentioned causes need to first be excluded. This is where the abnormal taste or bad taste is not due to any physical or physiologic problem but it a psychological manifestation.